The present invention relates to a seat belt retractor and to a seat belt arrangement incorporating such a retractor.
Motor vehicles are provided with seat belts to retain people travelling in such vehicles in their seats in the event of an accident arising. Ideally each seat belt should act to keep the person wearing the belt fully in their seat, without any significant forward movement relative to the seat, in order to minimise any . risk of the person hitting their head on the windshield or on the steering wheel.
It has been realised that if a safety belt is to perform correctly under accident conditions, the belt should be worn correctly, and in the case of the now conventional diagonal-and-lap belt, the belt should pass over the shoulder of the person wearing the belt and should then extend substantially horizontally to a point able to withstand the load created when an accident arises and the vehicle decelerates very rapidly.
Various proposals have been made regarding adjustable guides for seat belts to be mounted on the door pillars (or B-posts) of motor vehicles If such a guide is to be used the retractor reel is mounted on the floor adjacent to the B-post and the belt passes from the retractor through the guide over the shoulder of the person who is wearing the belt and then to a buckle, the belt then passing over the lap of the person wearing the belt to an anchoring point on the floor.
In one of these proposed guides there is an adjustment knob which can be operated to permit a carriage, which has a loop or guide through which the belt passes, to be slid up and down a vertical mounting rail which is secured to the B-post. See, for example, GB-2162045A which shows an arrangement of this type. If a person wearing the seat belt, for example the driver of the car, is to adjust the belt, he must turn his upper torso to be able to operate the adjustment knob, and then slide the carriage up or down. While he is in the necessary twisted position, the shoulder over which the belt will pass when in use, is not in the position that it will occupy ordinarily. Thus it is not possible to adjust the belt directly. Instead, an adjustment must be made, and the driver must return to the ordinary driving position before it can be ascertained whether the adjustment is correct or not. The procedure may need to be repeated several times before the adjustment is precisely correct. Of course, this adjustment cannot be carried out safely while driving, and thus the adjustment procedures must be completed before the driver starts to drive the car. Consequently, because the adjustment procedure is complicated and time-consuming, many drivers do not bother to make any adjustment at all, even though the facility for making an adjustment is provided. Thus such drivers may be driving with a safety belt which is ill-fitting and which will not provide an adequate degree of protection in the event of an accident.
It has been proposed to provide an automatically adjusting arrangement, in which a carriage is provided having a loop or guide through which the belt passes, the carriage being driven, by means of a motor, along a vertical rail mounted on the B.TM.post For example, the motor may drive a worm or screw that passes through a nut and is mounted on the carriage. The carriage can thus be driven up and down the rail. A position sensor may be provided to stop the carriage when it is sensed that the seat belt is in an optimum position. However, while such devices may operate in a very satisfactory manner, they are not cheap to produce, and thus such devices will only be commercially acceptable in very expensive cars.
Another problem that is encountered with safety belts is that of the stretch or resilience of the belt material. The safety belt material does stretch by a certain percentage of its length when subjected to the loads that can be experienced under accident conditions, especially if the person wearing the safety belt is heavy, or if the motor vehicle is subJected to severe deceleration from a high speed. In a typical safety belt of the diagonal-and-lap design, the length of safety belt that is exposed, and is thus available to stretch, approaches three meters. One end of the belt is located on the floor adjacent to the base of the B-post, and the belt passes from this end, across the lap of the person wearing the belt, to a tongue which is received in a releasable buckle. The belt then passes across the chest and over the shoulder of the person wearing the belt, finally passing through a guide at shoulder level and back down to floor level where it is received in the retractor reel. It is to be understood therefore that if such a belt is subjected to such a load that the belt is caused to stretch by ten per cent, then the total stretch will be approximately 30 cm. This degree of stretch will permit the person wearing the belt to move forwardly to a certain extent, and the person wearing the belt may then hit his head against the windshield or steering wheel.
The present invention seeks to provide a new retractor reel, which can be used in a seat belt arrangement, that provides an improvement over the prior art as discussed above.